The best way to kill time is to get a job. It may lead to tedium, but if you can chain your bonuses and keep a steady pace, soon you will rack up a great deal of money. Jobs are best done after shops have closed, so as to allow you to spend "dead" hours doing something productive and using the waking hours spending money at shops, upgrading your equipment or stocking your inventory. The rest of the day can be spent traversing the world, completing sub-quests and advancing amusing mini-games because nothing is intended to make you feel more accomplished than doing lots of little challenges. Rest can be had at intermittent times when so desired, but please keep in mind to choose a good resting spot because some places confer more advantages for using them than other areas. I personally prefer to posses several such hideaways so as to allow you to always have a nearby locale to cool down; trekking across town or countryside when low on energy can be dangerous, so having an extra home base or two is a good idea.